Ilmenite has served as a starting material for obtaining titanium dioxide of various degrees of purity. Generally when producing titanium dioxide by the sulphate route, it is important that ilmenite be as free of chromium as possible. It is also very essential that the purity of the raw ilmenite material be as high as possible so that the ilmenite may be used for other purposes. However, it is not only essential that ilmenite be pure for obtaining titanium dioxide by the above mentioned process but that it be substantially free of chromium when ilmenite is used for other purposes such as for producing titanium carbide which is suitable as a component in welding rod coatings as a precursor thereof.
Various investigations have heretofore been conducted for the separation of chromites from ilmenite and these have generally relied upon the magnetic properties of the chromite present in ilmenite.
The magnetic behavior of ilmenite and the susceptibility of the same to magnetic treatment is fairly well illustrated in the article authored by Westcott et al., Journal of Geophysical Research, Volume 73, No. 4, Pages 1269 to 1277 (1968) (Australian). Based on the disclosure in this article, the magnetic properties of ilmenite are fairly well understood such as the function of particle sizes as well as treatment of the same under oxidizing conditions.
Substantial laboratory investigation about the separation of chromites from ilmenite from various sources has been set forth in Investigation Report No. 461 dated Oct. 3, 1953 carried out under the auspices of Commonwealth Scientific and Research Organization in the Mining Department of the University of Melbourne. In that report, it has been concluded that magnetic separation of ilmenite is attractive especially if the ilmenite is treated under oxidizing conditions and the enhanced magnetic susceptibility of the ilmenite utilized to convert it to magnetically more active species vis-a-vis the chromite impurity in the ilmenite. In this article, it has been specifically mentioned that magnetic separation of the ilmenite prior to its oxidization and subsequent recovery of the chromite has not improved the recovery of ilmenite or enhanced the separation of chromites to the final chromium content required for a good quality sulphate feed stock.
Consequently, this article describes the separation of ilmenite to a degree which is still unacceptable for many purposes desired by the end users.